i) Field of the Invention:
The present invention relates to an automatic tool change system in a combined machining lathe, said system having a tool change arm for replacing tools between a turret and a tool magazine.
ii) Description of the Related Arts:
Conventionally, in a combined machining lathe, a turret often includes a first tool holding means for receiving a tool in a direction of the turret's rotation and a second tool holding means for receiving a tool in a direction of the turret's rotation plane. Hence, a tool change arm of an automatic tool change system is required to mount and demount the tools in the two different directions. For this purpose, one conventional automatic tool change system has been developed, as disclosed in Japanese Patent Laid-Open No. Sho 62-251040. In this system, as shown in FIGS. 7A and 7B, a tool change arm 101 has an L-shaped holding claw 102 rotatable around a rotation axis 103 inclined at an angle of 45.degree. with respect to a rotation axis 105 of a turret 104. When rotating 180.degree. around the rotation axis 103, the holding claw 102 can take an attitude where the holding claw 102 can insert or fit a tool into a first tool holding means 106 of the turret 104 (FIG. 7A) and an attitude where the holding claw 102 can insert or fit a tool into a second tool holding means 107 of the turret 104 (FIG. 7B). Hence, the tool change arm 101 meets the requirement of mounting and demounting of the tools into and out of the holding means of the two different directions.
In this conventional automatic tool change system, however, the tool change arm is required to have a mechanism for rotating the holding claw, and oil hydraulics for opening or closing the holding claw is supplied through a rotational part. As a result, its construction becomes complicated and its weight increases.